Semi-submersible vessels used in offshore oil operations can be large cumbersome vessels that need to be kept steady over a well site. They also need to be repositionable relative to certain defined coordinates. A need has existed for a removable and portable system for dynamically positioning semi-submersibles without the need for anchors, winches, or any type of anchor mooring device.
As oil and gas exploration is extending farther offshore into deeper water there is a need to make the semi-submersibles more mobile. Although for several years, a semi-submersible might sit in one location, they are mobile, and a need has existed for a way to move these massive structures.
Even in some shallow water areas, the use of anchor mooring systems may be prohibited, for instance, due to the presence of coral reefs or in locations where there already are multiple pipe lines and cables on the ocean floor and the use of anchors could damage the coral reefs or break existing pipe lines and cables.
A portable positioning system with portable thrusters, self-contained power units and a dedicated control system has long been needed, where the thrusters, power units and controls are not integral with any of the semi-submersible's systems or are integral with the hull of the semi-submersible and allow easy attachment to a pontoon at sea and easy removal at sea when the system is no longer required. A portable system is needed that can be removable such that it can reinstalled intact on another semi-submersible. This way, the thruster system can be leased to instead of owned by an operator, and at least theoretically lowering the cost of exploring for oil and gas, lowering the cost for a consumer.
Additionally, a need has existed for a modular system that can easily be increased or reduced in overall size and capacity to suit semi-submersible vessels of different sizes.
Additionally, a need has existed for a fully packaged, self-contained thruster system that is fully integrated, factory tested and class approved before installation on the semi-submersible, allowing vessel upgrades to dynamic positioning capability within just a short period of time, less than 3 months and as short as 60 days, at minimal cost, and a significant reduction from the 6 months to 1 year currently needed to retrofit semi-submersibles.
Additionally, a need has existed for a system which is easy to service at sea allowing minimal down time without the need for a semi-submersible to return to a yard or dry dock, allowing the semi-submersible to continue operating at its work location without interruption, hence increasing the profitability of the operation.
The present embodiments are detailed below with reference to the listed Figures.